This invention relates to fluid filters, and more particularly to fuel filters for vehicles.
Many types of fuel filters (also referred to as xe2x80x9cseparatorsxe2x80x9d) are known in the prior art. A popular type of fuel filter has a housing that encloses a replaceable ring-shaped filter element. The filter element ensures that impurities are removed from fuel before it is delivered to system components such as fuel injection pumps and fuel injectors. Mating portions of the housing form an interior enclosure for the element, and the housing portions may be separated for replacement of a spent filter element. Periodic replacement of the filter element is required so that the filter element will not become so loaded with impurities that fuel flow is restricted. Cost and ease of manufacture have been important considerations with such elements. However, problems may arise when such filter elements are replaced.
One problem is that filter elements with different sizes and/or filtration capabilities often have identical mounting configurations and can fit on the same filter head. However, use of the wrong filter can cause poor engine performance and allow undesirable amounts of contaminants to pass through the fuel system.
Another problem is that individuals may remove a spent filter element and simply re-attach the housing portions without a fresh element. While the engine may operate (at least for a short period of time), this can be detrimental to the engine.
A still further problem is that disturbance of the spent element during replacement may cause collected impurities to fall off the element. In some designs, these impurities may pass into the outlet of the filter housing and reach the components downstream in the fuel system.
To reduce and at least partially eliminate these problems, the filter assembly shown in U.S. Pat. No. 4,836,923, owned by the Assignee of the present application, was developed. This filter includes a unique replaceable filter element that is attached to a removable cover. The housing has an internal standpipe with an opening at the top end. When the element is removed from the housing, the fuel level in the housing falls below the opening in the standpipe. As a result, the impurity-laden fuel left in the housing is less likely to reach the outlet. Likewise, when a new element is installed in the housing, only fuel that has been purified by passing through the media of the element is enabled to reach the opening and pass out of the housing.
While this filter design has many advantages, if the filter element is not removed carefully, impurity-laden fuel in the housing or from the outer surface of the element may fall into the opening in the standpipe. If this happens, some impurities may still reach the downstream components of the fuel system.
In addition, the cover is discarded with each spent element. This is undesirable from a conservation and solid waste standpoint. It is generally desirable to minimize the amount of material discarded, particularly if a discarded element must be treated as hazardous waste. The cover also represents a portion of the cost of the replacement element. As a result this design adds cost to the replacement element. Further, the element may be separated from the cover, and the cover re-attached to the housing without a fresh element also being installed. As such, it still does not fully address the problems associated with operating an engine without a filter element installed.
A further improved filter is shown in U.S. Pat. No. 5,770,065, also owned by the assignee of the present application. In this filter, the filter element is received around a standpipe extending centrally in the housing. A spring-biased valve element internal to the standpipe is normally closed, and can be engaged and moved to an open position by a projection on the element when the element is properly installed in the housing. This filter provides the advantages of the ""923 patent, as well as prevents inpurity-laden fuel from passing through the standpipe when the element is changed. The assembly also prevents operation of the engine without an appropriate element in place.
The filter shown in the ""065 patent has received wide-spread acceptance in the marketplace. Nevertheless, it is believed that there exists a need for a still further filter which has the advantages of the ""065 patent, but where the valve structure is located exterior to the standpipe. Such a valve structure can be easier to manufacture and assemble, thereby reducing the cost of the assembly. It is also believed there is a demand for a filter where the opening into the standpipe is located toward the lower end of the filter. This can prevent or at least reduce the chance of pulling air into the system, as the opening is kept below the level of the fuel.
As such, it is believed that there exists a need for a further improved fuel filter which overcomes at least some of the above-described drawbacks.
A new and unique fuel filter is provided that prevents an improper filter element from being used in the filter and prevents operation of the filter without a filter element in place. The filter is simple and low-cost to manufacture and assemble, and prevents air from entering the system.
According to the present invention, a pipe extends centrally within the housing, and a valve structure is provided externally to the pipe. In one embodiment, the pipe is a standpipe fluidly connected to the outlet port; while in another embodiment the pipe is an inlet pipe to a fuel pump in the housing. In either embodiment, the pipe includes a central fluid passage and an opening into the passage toward the lower end of the pipe. A radially-outward facing groove or channel is provided circumferentially around the pipe, near the opening.
The valve structure for the filter includes a valve device and a latch device. The valve device has a sleeve closely surrounding the pipe, and an annular, radially-outward projecting base surrounding the sleeve. A series of radially-outward projecting tabs are spaced around the periphery of the base. The valve device can be easily manufactured unitarily in one piece from inexpensive material, such as plastic.
The latch device for the valve structure includes a series of deformable fingers in an annular array closely surrounding the pipe. The distal ends of the fingers are normally aligned with and engage the groove in the pipe to prevent the latch device from moving axially along the pipe. The latch device, in the locked position, supports the valve device in a position such that the valve sleeve blocks flow through the opening in the pipe. The latch device further includes an annular sleeve radially outwardly-spaced from the fingers. One end of the sleeve, located away from the valve device, is connected to the fingers, while the other end of the sleeve, located adjacent the valve device, defines an annular engagement surface. The latch device likewise can be easily manufactured in one piece from inexpensive material, such as plastic.
According to the first embodiment, the housing is designed for a xe2x80x9ctop-loadedxe2x80x9d element, and includes a removable lid. In this embodiment, the latch device is located between the valve device and the lower end of the housing, with the annular engagement surface of the latch device facing upwardly in the housing and against the base of the valve device.
In the second embodiment, the housing is designed for a xe2x80x9cbottom loadedxe2x80x9d element, and the latch device is located between the valve device and the pump, with the annular engagement surface of the latch device facing downwardly in the housing, and against the base of the valve device.
In either embodiment, a compression spring surrounds the pipe and urges the latch device toward the valve device.
The filter element for the fuel filter includes a ring of filter media circumscribing a central axis and having upper and lower end caps. Each end cap has an annular portion bonded to the end of the filter media. The lower end cap further has an axially-extending cylindrical portion connected to and bounding the inner diameter of the annular end cap portion, and an annular base projecting radially-inward from the cylindrical portion. The annular base closely surrounds the sleeve of the valve device in the first embodiment, and the inlet pipe in the second embodiment.
A plurality of thin, flat keys are provided internally of the cylindrical portion of the lower end cap. The keys project radially inward from the cylindrical portion toward the central axis, and axially away from the annular base. The keys project axially-outward (i.e., downward) from the media ring in the first embodiment (the xe2x80x9ctop-loaded designxe2x80x9d), and axially-inward (i.e., upward) into the media ring in the second embodiment (the xe2x80x9cbottom-loadedxe2x80x9d design). The keys preferably include a step defining an axially longer and radially thinner portion, and an axially shorter and radially wider portion. The lower end cap, including the cylindrical portion, base and keys, is also preferably formed unitarily, in one piece from inexpensive material, such as plastic.
In the first embodiment, when the filter element is inserted from the upper end of the housing, the keys of the lower end cap are received downwardly between the tabs on the valve device. The longer portions of the keys engage the upward-facing engagement surface on the latch device and cause the latch device to bend, which in turn causes the fingers to move radially outward from their locking engagement with the groove in the standpipe. At the same time, the shorter portions of the keys engage the base of the valve device and cause the valve device to move downwardly along the standpipe, against the latch device and out of blocking relation with the opening in the standpipe. When the element is properly positioned in the housing, the opening to the standpipe is completely open to allow fuel flow through the fuel filter.
In the second embodiment, when the element is bottom-loaded, the keys of the lower end cap are similarly received between the tabs on the valve device, with the longer portions of the keys engaging the downward-facing engagement surface on the latch device. This similarly causes the latch device to bend, and the fingers to move radially outward from their locking engagement with the groove in the pipe. The shorter portions of the keys at the same time engage the lower surface of the base of the valve device and cause the valve device to move upwardly along the pipe (against the latch device), uncovering the flow opening in the pipe. When the element is properly positioned in the housing, the opening to the inlet pipe is completely open to allow flow through the filter assembly.
The dimensions, number and location of the keys on the lower end cap and the tabs on the valve device can be selected to allow only a specific filter element to be used with a particular housing. An incorrect geometry, number or arrangement of keys and/or tabs will prevent a filter element from being properly located in the housing. The keys and tabs are relatively easy to fabricate, using simple molding operations.
Once a filter element with a proper selection of keys is installed in the housing, fluid can be provided into the housing and pass through the filter media ring to be filtered. When the element is to be replaced, the spring assists in removing the element from the housing, and returns the valve device to a position blocking the opening in the pipe. This prevents unfiltered fuel and contaminants from passing through the pipe and downstream in the system. The location of the opening in the lower end of the pipe is below the typical level of fuel in the housing, which prevents air from passing downstream through the system.
The valve device and latch device are easily assembled over the standpipe and inlet pipe during assembly of the filter housing.
Thus, as described above, the filter of the present invention provides many of the benefits of the prior art filters such as preventing an improper element from being installed within the housing, and preventing operation of the filter without and element in place. In addition, the filter is simple and low cost to manufacture and assemble, and prevents air from entering the system.
Further features and advantages will be apparent upon reviewing the following Detailed Description of the Preferred Embodiment and the accompanying Drawings.